I. Introduction
Due to recent developments in enabling technologies (biped walking control, mechatronics, computer technology) and findings in other fields like biomechanics, the development of humanoid robots is currently in an exciting phase. Prominent examples of sophisticated robots are Honda's Asimo [1], H7 from Tokyo University [2], HRP-2 from AIST and Kawada Industries [3], the world's first running biped QRIO from Sony [4], Wabian-2 from Waseda University [5] and the Korean robot HUBO from KAIST [6].